WO2014119720A1

WO2014119720A1 - Highly wear-resistant valve seat for use in internal combustion engine and manufacturing method therefor

Info

Publication number: WO2014119720A1
Application number: PCT/JP2014/052241
Authority: WO
Inventors: 聡史池見; 大重　公志; 佐藤　賢一
Original assignee: 日本ピストンリング株式会社
Priority date: 2013-01-31
Filing date: 2014-01-31
Publication date: 2014-08-07
Also published as: JP6290107B2; JPWO2014119720A1; BR112015018090A2; US10428700B2; US20150369090A1

Abstract

A highly wear-resistant valve seat for use in an internal combustion engine is provided. A feedstock powder for forming a valve-contacting-side layer is obtained by mixing an iron powder, a hard-particle powder, and a graphite powder. Said feedstock powder may also contain an alloy-element powder and/or a solid-lubricant-particle powder. The feedstock powder is formulated such that after sintering, a base part contains 0.3-2.0 mass% carbon and a total of up to 70 mass% of one or more of the following elements, with the remainder comprising iron and unavoidable impurities: cobalt, silicon, nickel, molybdenum, chromium, manganese, sulfur, tungsten, and vanadium. Some or all of the hard-particle powder has a mean particle diameter between 15 and 50 µm, inclusive, and the iron powder also has a mean particle diameter between 15 and 50 µm, inclusive, such that after sintering, the structure of the base part is such that hard particles constitute 10-65% of the total mass of the valve-contacting-side layer and are dispersed with a density of at least 1,000 particles/mm². This makes it possible to uniformly disperse a hard-particle phase throughout a base phase of a sintered body, yielding an iron-based sintered valve seat that exhibits excellent wear resistance and strength.

Description

Valve seat for internal combustion engine having excellent wear resistance and method for producing the same

The present invention relates to a one-layer or two-layer valve seat used for an internal combustion engine, and more particularly to further improvement of wear resistance.

In an internal combustion engine, a valve seat on which a valve for opening and closing an intake port and an exhaust port is seated can maintain the airtightness of a combustion chamber, and has wear resistance sufficient to withstand the wear caused by repeated contact of the valve. It is required to be retained. With the recent demand for higher output and improved fuel efficiency of internal combustion engines, valve seats are required to have further improved wear resistance. In particular, in gas engines such as CNG and LPG, and engines such as alcohol fuel, wear of valve seats is increased, and further improvement in wear resistance of valve seats is required.

In response to such a requirement, for example, Patent Document 1 describes a method of manufacturing a valve seat made of an Fe-based sintered alloy that exhibits excellent wear resistance. The technique described in Patent Document 1 is mass% as a raw material forming raw material powder, C: 0.5 to 1.5%, Ni: 0.1 to 3%, Mo: 0.5 to 3%, Co: 3 to 8%, Cr: Fe-based alloy powder containing 0.2 to 3%, the balance being Fe and inevitable impurities, and having an average particle size of 20 to 50 μm as a raw material powder for forming a hard dispersed phase in mass%, Mo: 20 to Co base alloy powder containing 32%, Cr: 5 to 10%, Si: 0.5 to 3%, the balance consisting of Co and inevitable impurities and an average particle size of 20 to 50 μm is used. The alloy powder is mixed in an amount of 25 to 35% by mass with respect to the total amount of the Fe-based alloy powder, and the mixed powder press-molded body is solid-phase sintered in a vacuum atmosphere to obtain C: Containing 0.5 to 1.5%, Ni: 0.1 to 3%, Mo: 0.5 to 3%, Co: 13 to 22%, Cr: 1 to 5%, Si: 0.1 to 1%, the balance being Fe and inevitable impurities Composed of An Fe-based sintered alloy base having a 10-20% porosity is uniformly formed on the ground, and the Mo-Fe-Co alloy hard dispersion phase is uniformly distributed. This is a technology to make a combined gold valve seat.

In addition, Patent Document 2 describes a method for manufacturing a wear-resistant sintered member. In the technique described in Patent Document 2, when the raw material powder containing the base forming powder and the hard forming powder is compacted and sintered, the base forming powder is made into a fine powder having a maximum particle size of 46 μm and 90% by mass or more. The formed powder is 40 to 70% by mass of the raw material powder. In the technique described in Patent Document 2, it is preferable that the base-forming powder is an iron-based alloy powder containing Cr: 11 to 13% by mass. Thereby, it is said that a sintered member having improved wear resistance and strength and excellent corrosion resistance can be obtained.

Patent Document 3 describes a method for manufacturing a sintered valve seat. In the technique described in Patent Document 3, a base-forming powder having a maximum particle size of 74 μm, a maximum particle size of 150 μm, Mo: 20 to 60 mass%, Cr: 3 to 12 mass%, Si: 1 to 5 mass% , And sintering the powder after compacting the raw material powder obtained by adding 40 to 70% by mass of the hard phase forming powder composed of Co and inevitable impurities and graphite powder: 0.8 to 2.0% by mass. It is a manufacturing method of a valve seat. The base forming powder preferably has a particle size configuration in which a powder having a particle size of 46 μm or less is 90% or more and a powder having a particle size of 74 μm or less is the balance. Further, as the base forming powder, it is preferable to use a steel powder containing a relatively large amount of Mo, Cr, Ni, V, Co or the like alone or in combination. In the invention described in Patent Document 3, the pores are filled with copper, copper alloy, lead, or lead alloy. Thereby, it is said that even higher wear resistance can be exhibited even under severe environments.

Patent Document 4 describes an iron-based sintered alloy material for a valve seat. The technique described in Patent Document 4 is an iron-based sintered alloy material in which two types of hard particles are dispersed and contained. The first hard particles are hard particles having an average primary particle size of 5 to 20 μm, and the second hard particles As the hard particles having an average primary particle diameter of 20 to 150 μm, among the particle diameters corresponding to the peak top positions of the mixed hard particles when these particles are mixed, the difference in the particle diameters of the adjacent peak top positions is The first and second hard particles are selectively used so as to be in the range of 15 to 100 μm, and the first hard particles and the second hard particles are blended so as to occupy 10 to 60 area% in total. Yes. Thereby, it is said that it is possible to simultaneously achieve improved wear resistance when used as a valve seat, reduced counter valve attack, and improved mechanical strength.

Japanese Patent Laid-Open No. 2004-124162 Japanese Unexamined Patent Publication No. 2007-107034 Japanese Unexamined Patent Publication No. 2007-113101 WO 2009/122985 A1

However, the techniques described in Patent Documents 1 to 3 use powder containing a relatively large amount of alloy elements such as Ni, Mo, Co, and Cr as the base forming powder. In addition, there was a problem that strength, machinability, density and the like were lowered.
In addition, in the technique described in Patent Document 4, when a large amount of fine hard particles are contained for further improvement of wear resistance, the hard particles are aggregated, and it is difficult to uniformly disperse, and also aggregate. There was a problem that hard particles became the starting point of wear.

The present invention solves such problems of the prior art, and provides a valve seat for an internal combustion engine having excellent wear resistance and crushing strength, in which hard particles are uniformly and finely dispersed in a matrix phase, and a method for producing the same. The purpose is to provide.

In order to achieve the above-described object, the present inventors diligently studied various factors that affect the dispersion of hard particles in the matrix phase. As a result, it has been found that the properties of the powder other than the hard particle powder greatly influence the dispersion of the hard particles.
Then, when trying to further improve the wear resistance by dispersing fine hard particles, if a large amount of fine hard particle powder is blended, the hard particles are likely to aggregate, and the dispersion of hard particles becomes rather rough. Found that there is a case. This was found to be prominent when iron-based powders for base formation such as pure iron powder and alloy steel powder were composed of coarse powders having a larger particle size than hard particle powders.

Therefore, in order to prevent hard particles from agglomerating and coarsely dispersing as a hard particle phase, the present inventors have determined that the hard particle powder blended in the mixed powder has an average particle diameter passing through a # 350 sieve. Is a fine powder (-# 350) having a particle size of 15-50 μm, and the average particle diameter of the base forming powder (iron-based powder) passing through the # 325 sieve is approximately the same as that of the hard particles described above. However, it was important to use a fine powder (-# 325) of 15 to 50 μm.

First, the experimental results on which the present invention is based will be described.
Iron powder, hard particle powder, graphite powder, alloy element powder, and solid lubricant powder are used as raw material powders, mixed with various types of raw material powders, and mixed with a V-type mixer. A and C. These mixed powders are charged into a mold and compression-molded with a mechanical press to form a single-layer valve seat-shaped green compact with a green density of 7.0 g / cm ^3. After the treatment and further pressure forming, a 2P2S process was performed in which a sintering treatment was performed at a sintering temperature of 1150 ° C. in a reducing atmosphere to obtain an iron-based sintered body. In addition, the mixed powder contains 100 parts by mass of the total amount of iron-based powder, alloy element powder, graphite powder, hard particle powder and solid lubricant powder as the lubricant particle powder, and 1.0 part by mass of zinc stearate. did.

In the mixed powder A, an iron-based powder, an alloy element powder, a graphite powder, a hard particle powder, and a solid lubricant powder are used, and the iron powder has an average particle size of 60 to 80 μm in mass% with respect to the total amount thereof. A total of 60% atomized pure iron powder and high-speed steel powder with an average particle size of 60-80μm, Co-based intermetallic compound powder with an average particle size of 5-20μm and Co with an average particle size of 20-150μm as hard particle powder A total of 35% of the intermetallic compound powder, 1.0% of the graphite powder, 2.0% of the Ni powder as the alloy element powder, and 2.0% of the MnS powder as the solid lubricant powder were mixed to obtain a mixed powder.

In the mixed powder C, iron-based powder, alloy element powder, graphite powder, hard particle powder, and solid lubricant powder are used, and the # 325 sieve is used as the iron-based powder in mass% with respect to the total amount thereof. A total of 60% atomized pure iron powder (-# 325) with an average particle diameter of 15-50 μm and high-speed steel powder (-# 325) with an average particle diameter of 15-50 μm is used as a hard particle powder. Solid lubricant powder with 35% Co-based intermetallic compound powder (-# 350) with an average particle size passing through 350 sieves of 35-50%, graphite powder 1.0%, Ni powder as alloy element powder 2.0% As a mixed powder, 2.0% of MnS powder was blended.

From the obtained iron-based sintered body, a valve seat (size shape: φ30 × φ21 × 8 mm) was processed by cutting and grinding, and a single rig wear test was performed using a single rig wear tester. In the single rig wear test, a valve seat was press-fitted into a jig equivalent to a cylinder head, and then the valve and the valve seat were heated by a heat source attached to the testing machine and the valve was moved up and down by a crank mechanism. The amount of wear was measured by the amount of valve sinking. The test conditions were as follows.

Test temperature: 300 ° C (sheet surface)
Test time: 6h
Cam rotation speed: 3000rpm
Valve speed: 20rpm
Spring load: 2940kgf (300N) (when set)
Valve material: T400 overlay material Lift amount: 9mm
The amount of LPG + Air and the amount of cooling water were constant.

Further, the obtained iron-based sintered body was processed into a valve seat (size and shape: φ28 × φ22 × 6.5 mm) by cutting and grinding, and the crushing strength was measured in accordance with JIS Z 2507.
From the obtained results, the wear resistance and the crushing strength are compared based on the iron-based sintered body (reference material) using the mixed powder A as a reference (1.00), and are shown in Table 1.

The iron-based sintered body using the mixed powder C has both increased wear resistance and crushing strength as compared to the reference material (iron-based sintered body using the mixed powder A).
Next, a specimen for observing the structure was collected from the obtained iron-based sintered body, the cross section was polished and corroded (corrosion liquid: marble liquid), and the structure was observed with an optical microscope. An example of the iron-based sintered body using the mixed powder A and the iron-based sintered body using the mixed powder C are shown in FIG. From FIG. 1, in the iron-based sintered body using the mixed powder A, the hard particles are aggregated to form a coarse hard particle phase. On the other hand, in the iron-based sintered body using the mixed powder C, hard particles are not aggregated, and the hard particle phase is relatively uniformly dispersed in the matrix.

From this experimental result, the hard particle powder to be mixed into the mixed powder was made into a fine hard particle powder (-# 350) with an average particle size of 15-50 μm, and the iron-based powder was made into a fine iron-based powder with an average particle size of 15-50 μm If the mixed powder blended as (− # 325) is used to form a sintered body, that is, both the iron-based powder and the hard particle powder are almost the same in average particle diameter, and the average particle diameter is 15 to 50 μm. It was found that the hard particle phase can be uniformly and finely dispersed in the matrix phase of the sintered body by blending it as a fine powder and further removing the large-diameter powder with a # 350 or # 325 sieve.

The present invention has been completed based on the above findings and further studies. That is, the gist of the present invention is as follows.
(1) A valve seat for an internal combustion engine made of an iron-based sintered body consisting of one layer or two integrated layers, wherein at least a layer on the valve contact surface side of the valve seat is C: 0.3 to 2.0. 1% or more selected from Co, Si, Ni, Mo, Cr, Mn, S, W, and V in total, and 70% or less in total, the balance being Fe and inevitable impurities wherein a base part composition, the hard particles comprise from 10 to 65% by mass% with respect to the layer the total amount of the valve contact surface side, and that it has a base portion structure comprising a rigid particles are dispersed 1000 / mm ² or more A valve seat for an internal combustion engine with excellent wear resistance.
(2) The valve seat for an internal combustion engine according to (1), wherein the hard particles are Co-based intermetallic compound particles or Fe-based intermetallic compound particles having a Vickers hardness HV _0.1 of 500 to 1200 HV.
(3) The valve seat for an internal combustion engine according to (2), wherein the Co-based intermetallic compound particles are Mo—Fe—Cr—Si Co-based intermetallic compound particles.
(4) In any one of (1) to (3), the solid lubricant particles are contained in the base part structure in an amount of 0.5 to 2.0% by mass based on the total amount of the layer on the surface side per valve. A valve seat for an internal combustion engine.
(5) In any one of (1) to (4), the seating surface side layer integrated with the valve contact surface side layer contains, in mass%, C: 0.3 to 2.0%, and the balance Fe and Base part composition consisting of inevitable impurities, or C: 0.3-2.0% by mass%, one or more selected from Mo, Si, Ni, Cr, Mn, S, W, V A valve seat for an internal combustion engine comprising a total base content of 10% or less, the balance being Fe and inevitable impurities.
(6) In the internal combustion engine according to (5), the solid lubricant particles are included in the matrix phase of the layer on the seating surface side in an amount of 0.5 to 2.0% by mass based on the total amount of the layer on the seating surface side. Valve seat.
(7) As a raw material powder, an iron-based powder, a hard particle powder, a graphite powder, or an alloy element powder, or a solid lubricant particle powder is blended and mixed to obtain a mixed powder, and the mixed powder is used as a mold. An internal combustion engine in which a green compact having a predetermined shape and density is formed by compression molding and sintered, and the green compact is sintered to obtain a valve seat made of an iron-based sintered body composed of one layer or two layers. A valve seat manufacturing method for forming a layer on at least a valve contact surface side of the valve seat, wherein the raw material powder has a base composition after sintering of mass% and C: 0.3 to 2.0%. A composition comprising 70% or less in total of one or more selected from Co, Si, Ni, Mo, Cr, Mn, S, W, and V, the balance being Fe and inevitable impurities The composition of the base portion after being mixed and the sintered material hits the bulb with the hard particles Comprises 10 to 65% by mass% with respect to the layer the total amount of the surface side and the rigid particles such that 1000 / mm ² or more distributed allowed comprising tissue, part or all of the hard particle powder, having an average particle size A method for producing a valve seat for an internal combustion engine having excellent wear resistance, characterized in that the powder is 15 to 50 μm and the iron-based powder is blended as a powder having an average particle size of 15 to 50 μm.
(8) The valve seat for an internal combustion engine according to (7), wherein the hard particle powder is a Co-based intermetallic compound powder or a Fe-based intermetallic compound powder having a Vickers hardness HV _0.1 of 500 to 1200 HV. Manufacturing method.
(9) A method for producing a valve seat for an internal combustion engine according to (8), wherein the Co-based intermetallic compound powder is a Mo—Fe—Cr—Si-based Co-based intermetallic compound powder.
(10) The mass of the solid lubricant particle powder according to any one of (7) to (9) with respect to the total amount of the layer on the surface side per valve side in the matrix phase of the layer on the surface side of the valve contact surface after sintering. %, And mixing so that it may become 0.5 to 2.0%.
(11) The method for manufacturing a valve seat for an internal combustion engine according to any one of (7) to (10), further comprising repeating molding and sintering at least once after the sintering.
(12) In any one of (7) to (11), the valve seat has a seating surface side layer integrated with the valve contact surface side layer, and for forming the seating surface side layer, The base composition of the layer on the seating surface side after sintering the mixed powder, the iron-based powder and the graphite powder as the raw material powder, or the alloy element powder, or further the solid lubricant particle powder, %, C: 0.3 to 2.0%, balance Fe and inevitable impurities composition, or mass%, C: 0.3 to 2.0%, Mo, Si, Ni, Cr, Mn, S, W, 1 type or 2 types or more selected from V are contained in a total of 10% or less, and the composition is composed of the balance Fe and inevitable impurities, and the iron-based powder has an average particle size of 60 Manufacturing method of valve seat for internal combustion engine, characterized in that mixed powder blended as powder of ~ 80μm Law.
(13) In (12), in the base of the layer on the seating surface side after sintering, the solid lubricant particle powder may be 0.5 to 2.0% by mass based on the total amount of the layer on the seating surface side. A method of manufacturing a valve seat for an internal combustion engine, comprising mixing.
(14) A valve seat for an internal combustion engine manufactured by the method for manufacturing a valve seat for an internal combustion engine according to any one of (7) to (13).

According to the present invention, it is possible to easily and inexpensively manufacture a valve seat for an internal combustion engine in which the hard particle phase is uniformly and finely dispersed in the matrix phase, the wear resistance is remarkably improved as compared with the conventional, and the strength is high. It has a remarkable industrial effect.

It is the optical microscope structure (b) in the sintered compact (valve seat) cross section, and its schematic diagram (a). It is a schematic diagram which shows the outline | summary of a single rig testing machine.

In the present invention, as the raw material powder, iron-based powder, graphite powder as alloy element powder, hard particle powder, or alloy element powder other than graphite, or further solid lubricant particle powder, or further lubricant Particle powder is blended and mixed to obtain a mixed powder. Then, the obtained mixed powder is inserted into a mold and compacted to obtain a compact having a predetermined shape and a predetermined density. Next, the green compact is sintered to obtain a valve seat made of an iron-based sintered body consisting of one layer or two upper and lower layers.

The mixed powder includes, as a raw material powder, an iron-based powder, a graphite powder as an alloy element, a hard particle powder, or an alloy element powder other than graphite, or a solid lubricant particle powder, or a further lubricant. Blend with particle powder.
In the present invention, the valve contact surface side layer of the valve seat is made of an iron-based sintered alloy having a base portion in which hard particles are dispersed in the base phase. By dispersing hard particles in the matrix phase, the wear resistance of the valve seat is significantly improved. Therefore, the hard particle powder to be blended is preferably a powder having a Vickers hardness HV _0.1 of 500 to 1200 HV. Examples of such powder include Co-based intermetallic compound powder, Fe-based intermetallic compound powder, and Fe-Mo hard particle powder. Among them, the Co-based intermetallic compound particles are particles in which a high hardness intermetallic compound is dispersed in a relatively soft Co matrix, and are preferable because they have a feature of low partner attack. Co-based intermetallic compound powders are Si-Cr-Mo-based Co-based intermetallic compounds, Si-Ni-Cr-Mo-based Co-based intermetallic compounds, and Mo-Fe-Cr-Si-based Co-based intermetallic compounds. However, examples of the Fe-based intermetallic compound powder include Co—Ni—Cr—Mo-based Fe-based intermetallic compounds. Incidentally, Co-based intermetallic compound particles, the hardness of the Fe-based intermetallic compound particles is preferably 500 ~ 1200 HV _0.1.
Among the Co-based intermetallic compound particles, Mo—Fe—Cr—Si-based Co-based intermetallic compound particles are particularly effective in improving wear resistance as hard particles. Mo-Fe-Cr-Si Co-based intermetallic compound particles are in mass%, Mo: 35-47%, Fe: 3-15%, Cr: 3-10%, Si: 2-5%, the balance Co and A composition comprising inevitable impurities is preferable.

Further, in the present invention, the base structure after sintering in the surface side layer per valve contains 10 to 65% of hard particles in mass% with respect to the total amount of the surface side layer per valve, and 1000 hard particles. / Mm ² Hard particles are blended so as to have a dispersed structure.
If the amount of hard particles dispersed is less than 10%, desired wear resistance cannot be ensured. On the other hand, if the dispersion exceeds 65%, the effect is saturated and an effect commensurate with the amount added cannot be expected. For this reason, the dispersion amount of the hard particles in the surface side layer per valve is limited to the range of 10 to 65% by mass% with respect to the total amount of the surface side layer per valve. More preferably, it is 30 to 40%.

In the present invention, the number of dispersed hard particles is used as an index of fine and uniform dispersion of the hard particles. In the present invention, in the valve-side surface side layer, the number of hard particles dispersed as described above is limited to 1000 / mm ² or more. When the number of hard particles to be dispersed is less than 1000 / mm ² , the hard particles are agglomerated and a significant improvement in wear resistance cannot be expected. For this reason, the number of dispersed hard particles is limited to 1000 / mm ² or more. It is preferably 1200 to 2000 pieces / mm ² .

The number of hard particles to be dispersed is determined by analyzing heavy metals contained in the hard particles using a scanning electron microscope equipped with an analyzer, taking an image of the image (COMP image), and determining the distribution of the hard particles. And the number per unit area is measured and obtained. In order to facilitate the measurement, the number is preferably binarized into a COMP image of heavy metal elements contained in the hard particles and a COMP image of other elements.

In addition to the above hard particles, the surface side layer per valve may further contain a solid lubricant in an amount of 0.5 to 2.0% by mass with respect to the total amount of the surface side layer per valve. If the content is less than 0.5%, a desired lubricating effect cannot be expected, and the machinability deteriorates. On the other hand, if the content exceeds 2.0%, the machinability improving effect is saturated and the strength is reduced. For this reason, when it is contained, it is preferably limited to the range of 0.5 to 2.0%. As solid lubricant, MnS, CaF ₂ can be exemplified.

Further, in the present invention, the mixed powder has a base part composition after sintering, for layer formation in the case of one layer or for layer formation on the valve contact surface side in the case of two integrated layers, Base phase and hard particles or solid lubricant particles as described above, C: 0.3-2.0%, further selected from Co, Si, Ni, Mo, Cr, Mn, S, W, V In addition, the raw material powder should be blended so as to contain 70% or less of one or two or more in total, and have a composition consisting of the remaining Fe and inevitable impurities.

The reason for limiting the composition of the base will be described. Here, “%” means mass% unless otherwise specified.
C: 0.3-2.0%
C is an element that increases the strength and hardness of the sintered body and facilitates the diffusion of metal atoms during sintering. In the present invention, C is preferably contained in an amount of 0.3% or more. On the other hand, when the content exceeds 2.0%, cementite is likely to be generated in the matrix, and a liquid phase is likely to be generated during sintering, resulting in a problem that dimensional accuracy is lowered. For this reason, C is limited to a range of 0.3 to 2.0%. Preferably, the content is 0.9 to 1.1%.

One or more selected from Co, Si, Ni, Mo, Cr, Mn, S, W, V: 70% or less in total Co, Si, Ni, Mo, Cr, Mn, S, W , V is an element that increases the strength and hardness of the sintered body and further improves the wear resistance. In order to obtain such an effect, at least one type including hard particle origin must be added. It is desirable to select and contain 25% or more in total. On the other hand, when the content of these elements exceeds 70% in total, the moldability is lowered and the strength is also lowered. For this reason, one or more selected from Co, Si, Ni, Mo, Cr, Mn, S, W, and V are limited to 70% or less in total. The total amount is preferably 60% or less, and more preferably 40% or less.

The balance of the valve-side surface layer other than the above components is composed of Fe and inevitable impurities.
In addition, the hard particle powder blended as a raw material powder in the mixed powder is dispersed in the matrix phase in the sintered body and contributes to improvement in wear resistance. As the hard particle powder to be blended is made finer, it tends to be finely dispersed in the matrix, and it is preferable to use as fine a powder as possible in order to improve wear resistance. Therefore, in the present invention, the hard particle powder is a fine hard particle powder having an average particle size of 15 to 50 μm (about-# 350) from the viewpoint of manufacturability, particularly fluidity. In addition, the average particle diameter measurement of powder shall use the value obtained using the laser diffraction method, for example.

In the present invention, the iron-based powder that is blended into the mixed powder as one of the raw material powders and constitutes the matrix is a powder that is approximately the same as the average particle diameter of the hard particle powder or has a finer average particle diameter. It is preferable. If the iron-based powder forming the base is larger than the average particle size of the hard particle powder, the hard particle powder is likely to aggregate, and it is difficult to uniformly and finely disperse the hard particle powder. Therefore, in the present invention, the iron-based powder to be blended is a powder having an average particle diameter of 15 to 50 μm, which is a powder having an average particle diameter substantially the same as that of the hard particles. The average particle diameter is preferably 25 to 35 μm.

Examples of the iron-based powder to be blended include atomized pure iron powder, alloy steel powder having a total amount of alloy elements of 5% by mass or less, and high-speed steel powder. These powders are preferably blended alone or in combination so as to be compatible with the base composition after sintering.
In addition to hard particle powder, solid lubricant powder, iron-based powder, powder mixed in mixed powder, for example, alloy element powder such as Ni powder, Co powder, graphite powder, from the viewpoint of finely dispersing hard particles, A powder having an average particle diameter of 15 to 50 μm is preferable. If the powder is larger than the average particle diameter, hard particles cannot be finely dispersed.

On the other hand, when the valve seat has a seating surface side layer (sitting surface side layer) integrated with the valve contact surface side layer, the seating surface side layer is bonded to the valve contact surface side layer by sintering. And is made of an iron-based sintered alloy in the same manner as the valve-side surface side layer. It is preferable that the seating surface side layer has a composition that does not contact the valve, supports the valve contact surface side layer, and can simply secure a desired strength as a valve seat.

For forming a layer on the seating surface side, it is preferable to use a mixed powder obtained by mixing and mixing iron-based powder and graphite powder, or further alloying element powder, or further solid lubricant particle powder as raw material powder. In this case, as the iron-based powder blended as the raw material powder, any powder similar to the surface side layer per valve is suitable, but atomized iron powder is preferable, and the average particle size is 60 to 80 μm. It is preferable to use powder.

Further, in the seating surface side layer, the solid lubricant particle powder may be contained in an amount of 0.5 to 2.0% by mass% with respect to the total amount of the seating surface side layer. If the content is less than 0.5%, a desired lubricating effect cannot be expected, and the machinability deteriorates. On the other hand, if the content exceeds 2.0%, the machinability improving effect is saturated and the strength is reduced. For this reason, when it is contained, it is preferably limited to the range of 0.5 to 2.0%. As solid lubricant, MnS, CaF ₂ can be exemplified.

The mixed powder for layer formation on the seating surface side has a matrix phase composition after sintering (in addition, a matrix composition including the solid lubricant particles when dispersed): C: 0.3 to 2.0% Or further containing 10% or less in total of one or more selected from Mo, Si, Ni, Cr, Mn, S, W, and V, from the remaining Fe and inevitable impurities It is preferable to mix the raw material powder so that the composition becomes.
The reason for limitation of the matrix phase composition after sintering of the seating surface side layer (the matrix part composition including the solid lubricant particles when dispersed) is as follows.

C: 0.3-2.0%
C is an element that increases the strength and hardness of the sintered body, and in the present invention, in order to ensure the desired strength and hardness as a valve seat, it is desirable to contain 0.3% or more in the seating surface side layer However, when the content exceeds 2.0%, cementite is likely to be generated in the matrix, and a liquid phase is likely to be generated during sintering, resulting in a problem that dimensional accuracy is lowered. Therefore, C is preferably limited to a range of 0.3 to 2.0%. More preferably, it is 0.9 to 1.1%.

The above-mentioned components are basic components of the seating surface side layer. In addition to this basic component, one selected from Mo, Si, Ni, Cr, Mn, S, W, and V is further selected as a selective element. You may contain 10% or less of seed | species or 2 or more types in total.
One or more selected from Mo, Si, Ni, Cr, Mn, S, W, V: 10% or less in total Mo, Si, Ni, Cr, Mn, S, W, V Is an element that increases the strength and hardness of the seating surface side layer, and can be selected as necessary and can contain one or more. In order to obtain such an effect, it is desirable to contain 1% or more in total, but even if the content of these elements exceeds 10% in total, the effect is saturated and an effect commensurate with the content is expected. It becomes impossible and it becomes economically disadvantageous. For this reason, when it contains, it is preferable to limit to 10% or less in total. More preferably, it is 5 to 6%.
The rest of the seating surface side layer other than those described above consists of Fe and inevitable impurities.

Next, a preferred method for forming the valve seat will be described.
In the present invention, it is preferable to use a press molding machine having a die, a core rod, an upper punch, a lower punch, and two types of feeders that can be driven independently of each other. Hereinafter, a valve seat composed of two layers of a valve contact surface side layer and a seating surface side layer will be described as an example.

First, the lower punch is relatively lowered, and a filling space for the seating surface side layer is formed by the lower punch, the die, and the core rod, and the first feeder is moved into the filling space to Fill with mixed powder. Next, the die and the core rod are raised relative to the lower punch to form a filling space for the valve contact surface side layer, and the second feeder is moved to the filling space to mix the valve contact surface side layer. Fill with powder. Then, the upper punch is lowered, and the mixed powder for the surface side layer and the mixed powder for the seating surface side layer are pressed together to form a green compact. The pressurizing conditions may be appropriately determined according to the need and need not be particularly limited, but in relation to the desired valve seat characteristics, the green compact density in the range of 5.0 to 7.5 g / cm ³ It is preferable to adjust so that it becomes.
The obtained green compact is then subjected to a sintering treatment to obtain a sintered body having an upper and lower two-layer structure. The conditions for the sintering process may be determined as appropriate according to the desired properties, except for performing in a reducing atmosphere, and need not be particularly limited. The sintering temperature is preferably 1100 to 1200 ° C. from the viewpoint of sintering diffusion.

From the viewpoint of securing strength, it is preferable to use a so-called 2P2S process in which the pressure molding and the sintering treatment are repeated at least twice. In the 2P2S process, the first sintering process is preferably presintering, and the second sintering process is preferably a sintered body having a desired density. Thereby, further improvement in density is expected. Further, instead of the 2P2S process, a forging-sintering process or an FS process in which a sintering process is performed after forging may be used.
Hereinafter, based on an Example, this invention is demonstrated further.

The raw material powders shown in Table 2 were blended in the blending amounts shown in Table 2 and kneaded with a V-type mixer to obtain various mixed powders for the surface side layer and mixed powder for the seating surface side per valve. In addition, Table 3 collectively shows the used iron-based powder, the type of hard particle powder, and the average particle diameter. The mixed powder No. A1 is a conventional blending example (conventional example).
These mixed powders were formed into a two-layered green compact using a press molding machine having a die, a core rod, an upper punch, a lower punch, and two types of feeders that can be driven independently of each other.

First, the lower punch is moved down relatively to form a filling space for the seating surface side layer with the lower punch, the die and the core rod, and the first feeder is moved into the filling space to mix the seating surface side layer. Filled with flour. Next, the die and the core rod are raised relative to the lower punch to form a filling space for the valve contact surface side layer, and the second feeder is moved to the filling space to mix the valve contact surface side layer. Filled with flour. Then, the upper punch was lowered, and the mixed powder for the surface side layer and the mixed powder for the seating surface side layer were integrally pressure-molded to obtain a two-layered green compact. In one part, a single layer of green compact was used. In that case, the first feeder was not used.

The obtained green compact is pre-sintered and further pressed with a powder molding machine (surface pressure: 6 to 10 ton / cm ² ), followed by sintering (1100 to 1200 ° C in a reducing atmosphere) 2P2S process is performed to obtain a sintered body. In some sintered bodies, a 1P1S process in which molding and sintering are performed once is used. Further, in some sintered bodies, an FS process in which a forging-sintering process is performed instead of the 2P2S process. The thickness of the sintered body was 8 mm, and in the case of two upper and lower layers, it was 1: 1.
Samples for analysis were taken from each layer of the obtained sintered body, and the content of each element was determined by emission analysis. The measurement was a cross section inside the boundary surface between the two layers.

Moreover, the density was measured about the obtained sintered compact using the Archimedes method.
Moreover, the obtained valve seat (sintered body) was inserted into a single rig wear tester shown in FIG. 2 and the following test conditions were tested. Test temperature: 300 ° C. (seat surface)
Test time: 6hr
Cam rotation speed: 3000rpm
Valve speed: 20rpm
Spring load: 2940kgf (300N) (when set)
Lift amount: 9mm
Valve material: T400 overlay material Note that the amount of LPG + Air and the amount of cooling water were constant.
The amount of wear (μm) was calculated by measuring the dent depth of the test piece (valve seat) after the test. The wear amount ratio of the sintered body was calculated based on the wear amount of the sintered body No. 1 as a reference (1.00). Abrasion resistance was evaluated by ◯ when the amount of wear was less than the standard, and x otherwise.

Further, the obtained iron-based sintered body was processed into a valve seat (size and shape: (φ28 × φ22 × 6.5 mm) by cutting and grinding, and the crushing strength was measured in accordance with JIS Z 2507. The crushing strength ratio of the sintered body was calculated using the crushing strength of the No. 1 as a reference (1.00), and the crushing strength was evaluated by ◯ when the crushing strength was higher than the reference, and x otherwise.

Table 4 and 5 show the obtained results.

The examples of the present invention are all valve seats (iron-based sintered bodies) that are superior in wear resistance and exhibit high crushing strength compared to the conventional example (sintered body No. 1). On the other hand, in comparative examples that are outside the scope of the present invention, the wear resistance is reduced, the crushing strength is reduced, or both are reduced.

1 Valve seat 2 Setting plate 3 Heat source (LPG + Air)
4 Valve

Claims

A valve seat for an internal combustion engine made of an iron-based sintered body consisting of one layer or two integrated layers, wherein at least a layer on the valve contact surface side of the valve seat includes C: 0.3 to 2.0% by mass A base composition comprising 70% or less of one or more selected from Co, Si, Ni, Mo, Cr, Mn, S, W, and V in total, with the balance being Fe and inevitable impurities If, resistance characterized by having a base portion structure comprising hard particles wherein comprising 10 to 65% by mass% with respect to the layer the total amount of the valve contact surface side, and to disperse the rigid particles 1000 / mm 2 or more Valve seat for internal combustion engines with excellent wear characteristics.
2. The valve seat for an internal combustion engine according to claim 1, wherein the hard particles are Co-based intermetallic compound particles or Fe-based intermetallic compound particles having a Vickers hardness HV 0.1 of 500 to 1200 HV.
The valve seat for an internal combustion engine according to claim 2, wherein the Co-based intermetallic compound particles are Mo-Fe-Cr-Si-based Co-based intermetallic compound particles.
4. The internal combustion engine for an internal combustion engine according to claim 1, wherein the solid lubricant particles are contained in the base portion structure in an amount of 0.5 to 2.0% by mass based on the total amount of the layer on the surface side per valve. Valve seat.
The seating surface side layer integrated with the valve contact surface side layer contains, in mass%, C: 0.3 to 2.0%, the base composition composed of the balance Fe and inevitable impurities, or C% in mass%. Contains 0.3-2.0%, contains one or more selected from Mo, Si, Ni, Cr, Mn, S, W, and V in total 10% or less, and balance Fe and inevitable impurities The valve seat for an internal combustion engine according to any one of claims 1 to 4, wherein the base seat composition has the following composition.
6. The valve seat for an internal combustion engine according to claim 5, wherein solid lubricant particles are included in the matrix phase of the layer on the seating surface side in an amount of 0.5 to 2.0% by mass based on the total amount of the layer on the seating surface side. .
As the raw material powder, iron-based powder, hard particle powder, graphite powder, or alloy element powder, or further solid lubricant particle powder are mixed and mixed to form a mixed powder, and the mixed powder is inserted into a mold. A valve seat for an internal combustion engine, which is compression molded to form a green compact having a predetermined shape and density, and sintering the green compact to form a valve seat made of an iron-based sintered body consisting of one layer or two layers. The raw material powder is used for forming a layer on at least the valve contact surface side of the valve seat, and the composition of the base part after sintering contains C: 0.3 to 2.0% by mass, Co: 1% or more selected from Si, Ni, Mo, Cr, Mn, S, W, V and 70% or less in total, so that the composition is composed of the remaining Fe and inevitable impurities The base structure after blending and sintering is a layer on the surface side of the valve per hard valve. Comprises 10 to 65% by mass% relative to the amount, and the rigid particles such that 1000 / mm 2 or more distributed allowed comprising tissue, part or all of the hard particles, the average particle size of 15 ~ 50 [mu] m A method for producing a valve seat for an internal combustion engine having excellent wear resistance, characterized in that the powder is mixed with the iron-based powder as a powder having an average particle size of 15 to 50 μm.
8. The valve seat for an internal combustion engine according to claim 7, wherein the hard particle powder is a Co-based intermetallic compound powder or a Fe-based intermetallic compound powder having a Vickers hardness HV 0.1 of 500 to 1200 HV. Method.
The method for producing a valve seat for an internal combustion engine according to claim 8, wherein the Co-based intermetallic compound powder is a Mo-Fe-Cr-Si-based Co-based intermetallic compound powder.
The solid lubricant particle powder is mixed in the matrix phase of the layer on the surface side per valve after sintering so that the mass% with respect to the total amount of the layer on the surface side per valve is 0.5 to 2.0%. A method for manufacturing a valve seat for an internal combustion engine according to any one of claims 7 to 9.
The method for manufacturing a valve seat for an internal combustion engine according to any one of claims 7 to 10, wherein after the sintering, molding and sintering are repeated at least once more.
The valve seat has a seating surface side layer integrated with the valve contact surface side layer. For forming the seating surface side layer, the mixed powder is used as the raw material powder, and iron-based powder and graphite powder. Or further alloying element powder, or further solid lubricant particle powder, the base part composition of the layer on the seating surface side after sintering contains C: 0.3 to 2.0% by mass, and the balance Fe and Composition of inevitable impurities, or mass%, including C: 0.3-2.0%, total of one or more selected from Mo, Si, Ni, Cr, Mn, S, W, V Characterized in that it is a mixed powder comprising 10% or less of the composition, the balance being Fe and inevitable impurities, and the iron-based powder blended as a powder having an average particle size of 60 to 80 μm. A method for manufacturing a valve seat for an internal combustion engine according to any one of claims 7 to 11.
The solid lubricant particle powder is mixed in the matrix phase of the layer on the seating surface side after sintering so as to be 0.5 to 2.0% by mass based on the total amount of the layer on the seating surface side. The manufacturing method of the valve seat for internal combustion engines of Claim 12.
An internal combustion engine valve seat manufactured by the internal combustion engine valve seat manufacturing method according to any one of claims 7 to 13.